where \(\langle \cdot , \cdot \rangle \)  denotes the Frobenius inner product and \(X \succeq 0\)  means that \(X\)  is positive semidefinite.
The feasible region of \(\text{P}_{(G,\sigma ,p)}\)  describes deformations of \((G,\sigma ,p)\) 
in the sense that \((G,\sigma ,q)\)  is a deformation of \((G,\sigma ,p)\)  if \(X=\operatorname{Gram}(q)\)  is feasible in \(\text{P}_{(G,\sigma ,p)}\) .
Hence, if \(\text{P}_{(G,\sigma ,p)}\)  has the unique solution (which must be \(X=\operatorname{Gram}(p)\) ), then \((G,\sigma ,p)\)  is globally rigid.
A tensegrity \((G,\sigma ,p)\)  having the property that \(\text{P}_{(G,\sigma ,p)}\)  has the unique solution is called universally rigid,
and the property has been extensively studied, see, e.g.,[1]}, [2]}.
